It is the fool who fails to return to the place of his last happiness

"It is the fool who fails to return to the place of his last happiness." - Don't know the author

Task tracking in eclipse

http://wiki.eclipse.org/Mylyn

Pretty useful eclipse tips

http://bogdanmocanu.wordpress.com/2008/02/29/eclipse-shortcuts-and-tips/

Multilayer validation strategy

The validation logic of an application can be spread across the application. Some logic against the UI, some against Business layer, some against service layer and some against DAO layer.

One difference between chapter 7 vs. 11 bankruptsy

Chapter 7 - Going into liquidation
Chapter 11 - Trying to re-habilitate

Simple APIs responsibilities on arguments

public Student createStudent(Student student, Couse course)

 

Lets say the responsibility of this API is to save the student and return the saved version back (the saved version will have the key).

 

Some implications of this API is that

1. If there is a failure, student and course objects should be left un-touched. If there were changes made before the createStudent() failed, all those changes should not be visible to the client of this API. This can be done by taking a copy of the student and course and letting createStudent() operate on that copy. That way if there is a failure, then the original student and course object remain intact.
2. If the operation succeeds, the client of this APIs would usually require that all changes made by createStudent() be reflected in student and course. To achieve this, after all createStudent operations complete successfully, overwrite the copy that was made at that start of the call back into student and course.

Salt lake city July 4th 2009 neighbourhood fireworks Part 2

One more

Salt Lake City July 4th 2009 neighbourhood fireworks

The view from my apartment's parking lot.

Do what you can do

Forget about your lists and do what you can because that’s all you can do. Phone up the people you miss and tell them you love them. Hug those close to you as hard as you can. Because you are always only a drunk driver’s stupidity, a nervous shopkeeper’s mistake, a doctor’s best attempts and an old age away from forever. - Julie

My hapiness and self worth

Don`t rely on someone else for your happiness and self worth. Only you can be responsible for that. If you can`t love and respect yourself - no one else will be able to make that happen. Accept who you are - completely; the good and the bad - and make changes as YOU see fit - not because you think someone else wants you to be different.

- Stacey Charter

Time it takes to get something done

Don’t let the fear of the time it will take to accomplish something stand in the way of your doing it. The time will pass anyway; we might just as well put that passing time to the best possible use
- Earl Nightingale

HQL notes

Source 

Case IN-sensitive

except names of classes and their properties
- Doubt: "This manual uses lowercase HQL keywords. Some users find queries with uppercase keywords more readable, but this convention is unsuitable for queries embedded in Java code." - why is this so? 

the from clause

minimum query is from Student - selects all instances of Student class. By default auto-import is true. So class names do not have to be qualified with the package name. If auto-import is turned off (false) then this query must be written as from com.xyz.Student 

To refer to Student in other parts of the query, an alias must be assigned to Student. from Student as student assigns student as an alias for Student. The "as" is optional. So the previous alias association can be written as from Student student. Its a good practice to start alias names in lower case as this is in-line with java coding standards for naming variable names.
- from Student as student, Department as department gives a cartesian product of all students and all departments. 

Joins

SQL Joins

Source. Joins used to fetch rows from 2 or more tables based on the relationship between columns in both the tables. Primary key is a column (or a group of columns - composite key) with unique values that identify each row. 

1. inner join - returns a row when there is a match in both the tables
2. left outer join - returns all rows from the left table even if there are no matches on the right table
3. right outer join - returns all rows from the right table even if there are no matches on the left table
4. full join - returns rows when there is a match in one of the tables

examples:

Employee table:

emp_no	emp_name	dept_no
1	xyz	1
2	abc	2
3	ghi	4

Department table:

dept_no	dept_name
1	IT
2	Sales
3	Accounts

inner join:

select emp.emp_no, emp.emp_name, dept.dept_name from employee as emp inner join department as dept on emp.dept_no = dept.dept_no;

emp_no	emp_name	dept_name
1	xyz	IT
2	abc	Sales

left outer join

select emp.emp_no, emp.emp_name, dept.dept_name from employee as emp left join department as dept on emp.dept_no = dept.dept_no;

emp_no	emp_name	dept_name
1	xyz	IT
2	abc	Sales
3	ghi

right outer join

select emp.emp_no, emp.emp_name, dept.dept_name from employee as emp right join department as dept on emp.dept_no = dept.dept_no;

emp_no	emp_name	dept_name
1	xyz	IT
2	abc	Sales
		Accounts

full join

select emp.emp_no, emp.emp_name, dept.dept_name from employee as emp full join department as dept on emp.dept_no = dept.dept_no;

emp_no	emp_name	dept_name
1	xyz	IT
2	abc	Sales
3	ghi
		Accounts

HQL Joins

Same types of joins as SQL

1. inner join e.g. from Employee as emp inner join | join emp.department as dept

2. left outer join e.g. from Employee as emp left outer join | left join emp.department as dept

3. right outer join e.g. from Employee as emp right outer join | right join emp.department as dept

4. full join

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Mapping reference